On Sat, 2019-01-26 at 11:09 -0800, Samuel Sieb wrote:
On 1/25/19 6:45 PM, Jonathan Ryshpan wrote:
> I'm using shred on some 2Tb USB disk drive that I plan to give away. So
> far it has taken 8 hours to shred 50% of the drive, which implies that
> it will take about 16 hours to shred the whole drive. I have another 2
> drives to go.
> Is there a quicker way to protect my data when I give the drives away,
> other than smashing the drives to bits?
I just checked the numbers and I think you're erasing as fast as you
can. That's a large hard drive and given the write speed of a spinning
disk, that's the time it will take. Can you not write them all at the
I'm pretty sure you're right. Here's what I've found out from a small
amount of research and experience.
(1) These two things
$ dd if=/dev/urandom of=/dev/sdc bs=1M status=progress
$ shred -v -n1 /dev/sdc
do the same thing, which is to overwrite the drive with random data in
a single pass.
They both do it at about the same speed, about 40Mbytes/sec., which is
probably about the max transfer rate to the drive. Another instance of
$ shred -v -n1 /dev/sdb
applied to an internal drive (which I also plan to dispose of) ran at
least twice as fast. Unfortunately I have no actual timings. Another
indication that the shredding rate is bounded by the transfer rate.
(2) Shred uses less cpu power, as closely as I could judge from a small
system monitor on my desktop.
(3) Since the time is bounded by the transfer rate, there's no
advantage to using /dev/zero instead of /dev/urandom; /dev/urandom is
slightly more secure.
(4) Repartitioning and reformatting the drive would almost surely be
good enough for my purposes; nevertheless it makes me nervous.
(5) Bottom line. Repartition and reformat if you think that's good
enough; otherwise use shred.
Thanks to all - jon